Recently, as a measure for implementing highly integrated and micropatterned semiconductor devices, an exposure apparatus using a charged-particle beam, such as an electron beam has been developed. The exposure apparatus has been considered to be unfit for mass-production until now, because of a low throughput.
However, the exposure apparatus is becoming a way to attain a practical throughput for mass-production by recent developments in a stencil mask type electron beam exposure apparatus and a multi-electron-beam exposure apparatus. Since these exposure apparatuses have a wider area to be exposed at once, i.e., an exposure area wider than that adopted in the prior art, throughput can be increased.
Unfortunately, in the stencil mask type charged-particle beam exposure apparatus, if the intensities of charged-particle beams, which strike the stencil mask are nonuniform in the irradiation region, the pattern to be transferred will deform. Furthermore, in the charged-particle beam exposure apparatus, a variation in intensities of a plurality of charged-particle beams will distort the pattern to be drawn. In particular, if a variation in intensities of charged-particle beams occurs due to a change in intensity distribution of the charged-particle beams during exposure, the drawing accuracy of the exposure apparatus greatly decreases.
To uniformly irradiate a wide range with beams by using the charged-particle exposure apparatus, a charged-particle beam source and optical system have been improved until now. However, irradiation uniformity achieved by such improvements is insufficient.
The irradiation intensity of a charged-particle beam irradiated from a charged-particle beam source often varies not only due to static intensity nonuniformity, but also due to the charged-particle beam source itself and an external environmental factor. The variation in irradiation intensity causes nonuniformity in the intensity distribution of charged-particle beams in the irradiation region, which is unpredictable by the charged-particle beam exposure apparatus, resulting in degradation in drawing accuracy.
In some cases, uniformity of the irradiation intensities of charged-particle beams is lost by replacing a charged-particle beam source or maintaining a certain structure associated with the beams.
Accordingly, a technique has been demanded to obtain statistically sufficient uniformity of the irradiation intensities, and to detect and to correct the irradiation intensity distribution of charged-particle beams during actual exposure in real time.
To meet this demand, as the technique for correcting a variation in intensities of charged particle beams in a charged-particle beam exposure apparatus, a method is proposed, which mounts apertures for irradiation current detection on an aperture array to detect the irradiation intensity distribution in real time (Japanese Patent Laid-Open No. 2004-193516). In addition, a method is proposed which manages the exposure time by controlling the blanker ON/OFF time (Japanese Patent Laid-Open No. 2003-051437). In the method of managing the exposure time by controlling the blanker ON/OFF time, to improve throughput, a blanker must be turned on/off under the control of the apparatus at a very high speed. However, the increase in throughput is limited due to difficulty in strict time management.